1. Field of the Invention
The invention relates to a contactless power transmitting device, a contactless power receiving device and a contactless power transfer system.
2. Description of Related Art
In recent years, a technique for contactlessly transmitting or receiving power to or from a device becomes a focus of attention because of less expense in time and effort for connection, or the like. Contactless charging is in practical use for charging a portable device, an electric vehicle, or the like.
Japanese Patent Application Publication No. 2011-15549 (JP 2011-15549 A) describes an example of a position aligning technique for a contactless power transfer device for a vehicle. In this example, a spatial position is acquired through an image captured by a camera for capturing an area behind the vehicle, and the vehicle is guided to a parking position or the vehicle is automatically parked.
JP 2011-15549 A does not describe the details of coil units that are used to transmit and receive electric power. Coil units of a plurality of types have been studied for use in a power transmitting unit and a power receiving unit.
In contactless power supply, a magnetic flux distribution that is generated in a coil unit or a magnetic flux distribution suitable for a coil unit to receive electric power varies on the basis of a coil shape, a winding method, a magnetic core shape, and the like. When the magnetic flux distributions of a pair of power transmitting portion and power receiving portion are different from each other, it is not possible to efficiently transmit or receive electric power. It is inconvenient that electric power cannot be transmitted or received at all because of a mismatch between the magnetic flux distribution of the power transmitting portion and the magnetic flux distribution of the power receiving portion.
Depending on a coil type, the transfer efficiency may be higher when there is a positional deviation than when there is no positional deviation. Therefore, when a power receiving device is guided to the same position irrespective of a coil type, it may lead to a case where the transfer efficiency deteriorates.